The present invention relates to a camshaft adjusting device.
Camshaft adjusting devices are generally used in valve train assemblies of internal combustion engines to vary the valve opening and closing times, whereby the consumption values of the internal combustion engine and the operating behavior in general may be improved.
One specific embodiment of the camshaft adjusting device, which has been proven and tested in practice, includes a vane adjuster having a stator and a rotor, which delimit an annular space, which is divided into multiple working chambers by projections and vanes. A pressure medium may be optionally applied to the working chambers, which is supplied to the working chambers on one side of the vanes of the rotor from a pressure medium reservoir in a pressure medium circuit via a pressure medium pump, and which is fed back into the pressure medium reservoir from the working chambers on the particular other side of the vanes. The working chambers whose volume is increased have an operating direction which is opposite the operating direction of the working chambers whose volume is decreased. As a result, the operating direction means that an application of pressure medium to the particular group of working chambers induces a rotation of the rotor relative to the stator either in the clockwise or the counterclockwise direction. The control of the pressure medium flow, and thus the adjusting movement of the camshaft adjusting device, takes place, e.g., with the aid of a central valve having a complex structure of flow-through openings and control edges, and a valve body, which is movable within the central valve and which closes or unblocks the flow-through openings as a function of its position.
One problem with camshaft adjusting devices of this type is that the camshaft adjusting devices are not yet completely filled with pressure medium in a start phase or may even have been emptied, so that, due to the alternating torques applied by the camshaft, the rotor may execute uncontrolled movements relative to the stator, which may result in increased wear and an undesirable noise development. To avoid this problem, it is known to provide a locking device between the rotor and the stator, which locks the rotor when the internal combustion engine is turned off in a rotation angle position with respect to the stator which is favorable for startup. In exceptional cases, for example if the internal combustion engine is stalled, it is possible, however, that the locking device does not properly lock the rotor, and the camshaft adjuster must be operated with an unlocked rotor in the subsequent start phase. However, since some internal combustion engines have a very poor start behavior if the rotor is not locked in the central position, the rotor must then be automatically rotated into the central locking position and locked in the start phase.
Such an automatic rotation and locking of the rotor with respect to the stator are known, for example, from DE 10 2008 011 915 A1 and from DE 10 2008 011 916 A1. Both locking devices described therein include a plurality of spring-loaded locking pins, which successively lock into locking gates provided on the sealing cover or the stator when the rotor rotates and which each permit a rotation of the rotor in the direction of the central locking position before reaching the central locking position while blocking a rotation of the rotor in the opposite direction. After the internal combustion engine has warmed up and/or the camshaft adjuster has been completely filled with pressure medium, the locking pins are forced out of the locking gates, actuated by the pressure medium, so that the rotor is subsequently able to properly rotate with respect to the stator to adjust the rotation angle position of the camshaft.
One disadvantage of this approach is that the locking of the rotor may be accomplished only with the aid of multiple successively locking locking pins, which results in higher costs. In addition, the locking procedure requires that the locking pins lock successively in a fail-safe manner. If one of the locking pins does not lock, the locking procedure may be interrupted, since the rotor is thus not locked in the intermediate position on one side and is unable to rotate back.
[An object of the present invention is therefore to provide a camshaft adjuster which has a fail-safe and cost-effective central locking of the rotor.
According to the basic idea of the present invention, the check valve is provided outside the locking pin in the rotor. Due to the check valve, the pressure medium is able to flow into the enlarging working chamber without it being able to be forced back out of this working chamber in the case of a torque acting upon the camshaft and oriented in the opposite direction. The check valve thus effectively forms a type of freewheel, which uses the active alternating torque to automatically rotate the rotor in a pulsating manner from the direction of the stop position in the direction of the central locking position. It is particularly important that the remaining working chambers are short-circuited during the inflow of the pressure medium, so that the pressure medium contained therein is able to flow over between the other working chambers and does not hinder the rotational movement. The check valve is preferably situated in a rotor hub of the rotor and outside the locking pin. The advantage of such an arrangement of the check valve is that the check valve does not have to be integrated into the locking pin, which is difficult to implement structurally, due to the limited installation space. Moreover, positioning the check valve in the rotor hub in spatial proximity to the locking pin enables pressure medium to flow through the check valve as a function of the position of the locking pin, even with a simple guidance of the pressure medium lines.
It is furthermore proposed that at least two valve devices are provided. Due to the two valve devices, two check valves may be switched as needed between two oppositely acting working chambers as a function of the particular assigned valve device. Central locking devices known from the prior art usually include a first and a second locking pin. Depending on whether the camshaft adjusting device is moved into the central locking position from the “advance” or “retard” direction, only one locking pin is in a first switching position in each case, since the other locking pin is held in a second switching position by the locking gate. The valve device is preferably formed by the locking pins and a receiving chamber which guides the locking pin. Alternatively, the position of the locking pin may be used to control a separate valve device, which is not formed by the locking pin and the receiving chamber. Due to the two valve devices, a first or a second check valve may thus be fluidically connected to two oppositely acting working chambers as a function of the position of the locking pins—and thus as a function of the rotation direction.
It is furthermore preferred that the adjacent first pressure medium line is divided into a pressure medium line having a check valve and a second pressure medium line with a free flow-through. Due to this arrangement of the pressure medium line, the check valve may be situated in the rotor hub and does not have to be accommodated in the locking pin. This results in the advantage that, with the aid of the position of the locking pin, a fluidic connection of a first pressure medium line may be established to a second pressure medium line via a fourth pressure medium line with a free flow-through or a third pressure medium line having a check valve. A 3/2-way valve is preferably used for this purpose. In a first switching position of the valve device, the first pressure medium line is fluidically connected to the second pressure medium line via the third pressure medium line having the check valve, while in a second switching position of the valve device, the first pressure medium line is fluidically connected to the second pressure medium line via the fourth pressure medium line with a free flow-through. In this context, a pressure medium line with a free flow-through is understood to be a pressure medium line, through which pressure medium may flow unhindered or essentially unhindered in both flow directions; a pressure medium therefore is unable to flow freely through a pressure medium line having a check valve.
It is furthermore proposed that a pressure medium line having a check valve is provided at at least two of the valve devices. In that at least two check valves are fluidically connected to one valve device, it is possible for the movement from the “advance” and “retard” positions into the central locking position to fluidically switch a different check valve between two working chambers having different operating directions. The operating direction of a first check valve is set in such a way that the fluidic connection of two oppositely acting working chambers is facilitated only with a movement from the “retard” position into the central locking position. In a second check valve, the operating direction is set in such a way that the fluidic connection of two oppositely acting working chambers is facilitated only with a movement from the “advance” position into the central locking position.
It is furthermore proposed that at least one of the working chambers, whose volume is decreased during a rotation of the rotor from the direction of one of the “advance” or “retard” stop positions in the direction of the central locking position, is fluidically short-circuited with another working chamber having the opposite operating direction, if at least one valve device is in the second switching position. This prevents the movement of the camshaft adjusting device from becoming blocked during a movement into the central locking position.
It is furthermore advantageous if a back-flow of the pressure medium from at least one of the additional working chambers is prevented by the check valve. Due to the two valve devices, the fluidic connection of two oppositely acting working chambers may be set via a check valve in such a way that the rotor is able to rotate relative to the stator in one direction in the start phase, due to the active alternating torques (camshaft torque actuated), while the rotational movement in the particular other direction is blocked by the check valve. The check valve thus virtually forms a type of freewheel, which uses the active alternating torque to automatically rotate the rotor in a pulsating manner from the direction of the stop position in the direction of the central locking position. It is particularly important that the remaining working chambers are short-circuited during the inflow of the pressure medium, so that the pressure medium contained therein is able to flow over between the other working chambers and does not hinder the rotational movement.
It is advantageous if at least one working chamber, whose volume is increased during the controlled adjustment of the stator relative to the rotor, is fluidically connected by the valve device to pressure medium pump P. This ensures that a controlled setting of the relative angle between the stator and the rotor may be established. For this purpose, the pressure medium pump is connected to at least one working chamber of an operating direction, whose volume increases during the adjusting movement. Due to the fluidic connection of the pressure medium pump to the working chamber via the valve device, it is ensured that the connection to the working chamber is established via the check valve as soon as the pressure medium line is depressurized. As a result, the residual pressure in the pressure medium line is used to move the camshaft adjuster in the direction of the central locking position when the internal combustion engine is turned off.
It is furthermore advantageous if at least one working chamber, whose volume decreases during the controlled adjustment of the stator relative to the rotor, is fluidically connected to pressure medium reservoir T. Due to the fluidic connection of the working chamber, whose volume decreases during an adjusting movement, to the pressure medium reservoir, the excess pressure medium may flow out.
The present invention is explained in greater detail below on the basis of one preferred exemplary embodiment. The following are shown in detail in the figures:
A camshaft adjusting device having a known basic structure with a schematically illustrated vane adjuster as a basic component is apparent from
A pressure medium circuit is also apparent, which includes a large number of pressure medium lines 1, 3, 4, 6, 8, 13, 14, 15, 18, 27, 28, 29, 31, 32, 33, 34, 38, 39, 40, 41 and 42, which are fluidically connectable to pressure medium pump P or pressure medium reservoir T via multi-way switching valve 7.
Stator 16 includes a plurality of stator webs, which divide an annular space between stator 16 and rotor 17 into pressure chambers 24 and 25. Pressure chambers 24 and 25, in turn, are divided by vanes 11 and 12 of rotor 17 into working chambers 20, 21, 22 and 23, into which pressure medium lines 1, 3, 4 and 6 open. Central locking device 26 includes two locking pins 2 and 5, which lock into a stator-fixed locking gate 19 for the purpose of locking rotor 17 with respect to stator 16. Locking gate 19 may be situated, for example, in a sealing cover screwed to stator 16.
In principle, the rotation angle of the camshaft with respect to the crankshaft during normal operation, i.e., in the “retard” direction, is adjusted by the fact that pressure medium is applied to working chambers 21 and 23, thereby increasing their volume, while the pressure medium is simultaneously forced out of working chambers 20 and 22, which reduces their volume (see
A valve function pin 35 is furthermore provided, which is also linearly shiftable and spring-loaded. Valve function pin 35 is spring-loaded in the direction of the position of engagement with locking gate 19 and is situated with rotor 17 in such a way that it does not hinder the rotational movement of rotor 17 with respect to stator 16. Valve function pin 35 is virtually only carried along. To enable rotor 17 to be adjusted with respect to stator 16, central locking device 26 is first released by applying pressure medium to locking gate 19 via pressure medium line 18 from the C port of multi-way switching valve 7 with the aid of pressure medium pump P. By applying pressure medium to locking gate 19, locking pins 2 and 5, as well as valve function pin 35, are forced out of locking gate 19, so that rotor 17 is able to subsequently rotate freely with respect to stator 16. To this extent, the camshaft adjusting device corresponds to the prior art.
It is apparent in
Locking pins 2 and 5 are spring-loaded in the direction of a first switching position, in which they engage with locking gate 19, as is apparent on the basis of locking pin 2 in
During the start phase of the internal combustion engine, alternating torques act upon the camshaft and thus also upon rotor 17. The torques acting upon rotor 17 in the direction of the arrow result in the fact that the pressure medium is forced out of working chambers 21 and 23 via pressure medium lines 3 and 6. When rotor 17 moves from the “retard” direction into the central locking position, locking pin 5 is in the second switching position, whereby fourth pressure medium line 32 is fluidically connected to second pressure medium line 33 via pressure medium line 41 (see
Working chambers 20, 21, 22 and 23 are thus short-circuited when torques occur in the direction of the arrow in
The reverse rotational movement of rotor 17 from the direction of the “advance” stop position in the direction of the central locking position is apparent in
In
Valve function pin 35 is in the second switching position and thus fluidically separates pressure medium lines 15 and 34 from each other. The pressure medium is thus no longer able to flow over between working chambers 20, 21, 22 and 23 of different operating directions. The pressure medium is then introduced from the B port into working chamber 23 via pressure medium lines 28 and 6 and into working chamber 21 via pressure medium lines 28, 29, 33, 41, 32 and 3, so that the volume of working chambers 21 and 23 is increased. At the same time, the pressure medium flows back into pressure medium reservoir T from working chamber 20 via pressure medium lines 1, 13, 39, 14, 27 and from working chamber 22 via pressure medium lines 4 and 27 with the aid of the A port of multi-way switching valve 7, so that the volume of working chambers 20 and 22 is decreased. Due to the changes in volume of working chambers 20, 21, 22 and 23, rotor 17, including vanes 11 and 12, is rotated to the left with respect to stator 16 in the direction of the arrow in the top developed view.
Valve devices 36 and 37 are preferably designed as a 3/2-way valve, as illustrated in
In the exemplary embodiment illustrated in
Number | Date | Country | Kind |
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10 2014 205 569 | Mar 2014 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/DE2015/200000 | 1/12/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2015/144140 | 10/1/2015 | WO | A |
Number | Name | Date | Kind |
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8205586 | Strauss et al. | Jun 2012 | B2 |
8640662 | Cole et al. | Feb 2014 | B2 |
8752516 | Takada | Jun 2014 | B2 |
8800512 | Strauss | Aug 2014 | B2 |
9765655 | Zschieschang | Sep 2017 | B2 |
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1061470 | May 1992 | CN |
102007007072 | Aug 2008 | DE |
102008008005 | Aug 2009 | DE |
102008011915 | Sep 2009 | DE |
102008011916 | Sep 2009 | DE |
102009002805 | Nov 2010 | DE |
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WO2012094324 | Jul 2012 | WO |
Number | Date | Country | |
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20170096915 A1 | Apr 2017 | US |